Such a robot, which is known from US-A1-2006/0273749 can be used for cleaning areas for example by means of vacuum cleaning.
Such kind of a robot preferably comprises a energy storage by means of which power can be supplied to several components of the robot like a vacuum cleaner, a propelling unit for moving the robot and for example a sensor for the detecting obstacles in the neighbourhood of the robot.
For example when the charging level of the energy storage is lower than a predetermined reference level, the robot must return to the base station to recharge the energy storage. Another reason for returning to the base station might be to empty a dust container or to refill a water container.
To be able to find the base station, the base station comprises a signal emitting module which signal is being detected by a sensor of the robot. As soon as the base station has been detected, the robot is moved back under the control of the processor to the base station. For moving the robot back to the base station it is not necessary to know the absolute position of the robot with respect to the base station. Due to the signal emitted by the signal emitting module of the base station, the direction to which the robot should be moved is known.
After recharging the energy storage, the robot should resume the vacuum cleaning or other operation it was performing before being interrupted.
If the robot resumes its operation from the base station the area around the base station will be cleaned again and the area in the neighbourhood of the position where the cleaning operation was interrupted will not be cleaned at all.
However since the absolute position of the robot at the moment that the operation of the robot was interrupted is not known, it is not possible to resume the operation from the interrupt location.
To provide the robot with means for sensing, detecting and memorizing constantly the absolute position of the robot with respect to the base station to be able to move the robot back to the interrupt location, is relatively costly and complicated.